Several types of marine hoisting systems are in common use for retrieving loads such as crab and shrimp pots, lobster traps, and the like from marine environments. Such hoisting systems generally utilize some type of a rotating shaft such as a capstan, roller or sheave assembly around which a line is lead for retrieval. Safety, reliability and convenience are important factors.
One type of hoisting system utilizes a gasoline-powered engine having a gear reduction unit that rotates a capstan drive. The line is wrapped several times around the capstan, and hoisting friction is obtained by maintaining constant tension on the free end of the line. This system requires constant operator involvement. One of the serious safety deficiencies of this type of gasoline engine-powered hoisting system is that the capstan can be stopped only by shutting off the engine. Despite constant attention from an operator, the line frequently becomes tangled as it is retrieved. Because the capstan cannot be easily turned off in an emergency situation, many operators panic and grab at the entangled line, while the capstan continues to rotate, resulting in serious injury. Lead weights, which may be attached at intervals on the lines, also tend to hit the block leading to the capstan and fly off unpredictably, sometimes injuring the operator.
Gasoline engine powered hoisting systems are difficult to refuel, particularly when the vessel is on the water. Gasoline spills may cause fires or explosions, and both spills and exhaust pollute the environment. Moreover, operation of gasoline-powered auxiliary engines requires regular maintenance, is noisy during operation, produces unpleasant exhaust, and generally do not provide reliable starting. Typical gasoline engines also quickly corrode, particularly during exposure to marine salt-water environments.
Hydraulic hoisting systems generally provide safer operation than the gasoline-powered systems, but they require installation of a hydraulic pump on the vessel, with the associated hydraulic lines, valves, and the like. Hydraulic systems require a substantial initial investment, are heavy, and have substantial maintenance requirements. Hydraulic hauling systems are well suited to larger, commercial vessels, but are too costly and heavy for smaller, recreational and light commercial applications.
U.S. Pat. No. 4,234,164 discloses a gasoline motor powered crab pot hauling system utilizing a specialized sheave assembly. The sheave comprises a pair of separated flywheels having wear resistant replaceable sheave inserts. The replaceable inserts are corrosion and wear resistant, and can be made of a light weight and inexpensive material. The inserts may be made of stamped stainless steel, cast iron or a thermosetting plastic such as phenolic [sic]. The sheave inserts are disc-like and frusto-conical in shape and abuttingly engage and form a groove for receiving the line to be hauled. This approach requires the use of a line separator or stripper to separate the line from the running bight of the sheave.
U.S. Pat. No. 4,165,830 discloses a crab pot warp line coiler. The hauling block is suspended from a davit projecting outwardly from a location above the rail of a vessel and comprises a sheave rotated by a hydraulic drive source with fairlead sheaves leading the pot line toward and away from the drive sheave. The drive sheave has a deep V-groove for wedgingly receiving the pot line. A shock absorber is provided between the davit and the hauling block to stabilize the hauling block and provide the desired degree of alignment, while allowing the hauling block to have some freedom of motion.
U.S. Pat. No. 3,765,614 discloses a hydraulically operated line hauling and coiling apparatus in which line is passed through a fairlead mechanism to a V-shaped groove in the drive sheave. The line is then stripped from the drive sheave and conveyed to the coiling system.
U.S. Pat. No. 3,722,126 discloses a marine hauling apparatus in which a gangion block is positioned over the side of the vessel and mounted with a rotational joint for continuously lifting line from the sea. The block has two identical sheave members mounted on a frame for independent rotation about a common axis. Each of the sheave members has a peripheral surface flared radially from an inner rim edge to an outer rim edge, the flare forming a conical surface. The sheave members are mounted in face-to-face relationship to form a peripheral groove between the two flared surfaces with a clearance space between the inner rim edges. A second gangion block on the vessel receives the line from the first block and uniformly positions both the line and the harvesting devices suspended from it for further handling on the vessel.
U.S. Pat. No. 3,942,655 discloses a lobster trap davit for hoisting lobster traps from water onto a gunnel of a lobster boat. The hoist arm of the davit is adjustable and is pivotable in a vertical plane. The davit may be operated using electrical, hydraulic or pneumatic means.
Although numerous marine hauling systems are known in the art, as evidenced by the patents described above, none of them provides convenient, safe operation for recreational and light commercial applications.